Safety control system for fuel burners



N w, 14-. c. K. STROBEL SAFETY CONTROL SYSTEM FOR FUEL BURNERS FiledMarch 2, @945 14 ,2 155 22 fig)? lg 52 -1- I T I INVENTOR. 154(fianlerffiSiPflb H13 Arramvzr.

Patented Nov. 30, 1948 SAFETY CONTROL SYSTEM FOR FUEL BURNERS Charles K.Strobel, Pittsburgh, Pa., asslgnor to Robertshaw-Fuiton (JontrolsCompany, a corporation of Delaware Application March 2, 1945, Serial No.580,672 Claims. (Cl. 158-117.!)

1 This invention relates to safety control and ignition systems forgaseous fuel burners and, more particularly, to electrical systemstherefor.

In apparatus of this general character, the flow of fuel to a mainburner may be controlled by an electromagnetic control device which isenergzcd by the current generated by a thermocouple c-r thermopileresponsive to the heat of a flame at the pilot burner. Means areemployed for placing the armature of the electromagnet in attractedposition and the fuel control device in a flow permitting position suchoperation being generally termed resetting." ployed for resetting may beelectrically operated from a source of current separate from thatgenerated by the thermocouple. It is apparent that once the resettingoperation is' completed the current from this separate source is nolonger required and the system may be left under the sole control of thethermoelectric current which is generated as long as the pilot burnerproduces a fiama- An object of this invention is to reset anelectromagnetic device by electrically operated means which areautomatically rendered inoperative upon completion of the resettingoperation.

Another object of the invention is to energize an electric igniter forthe pilot burner from the same source of current as is used forenergizing the resetting means. 8

Another object of the invention is to associate The means 8111-."

various elements of the control system in compact units requiring aminimum number of operations to place the system in running condition.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawings,

wherein:

Fig. 1 is a schematic embodiment of the safety control and ignitionsystem of this invention in conjunction with the main and pilot burnersof a gaseous fuel burning apparatus; and

Fig. 2 is a similar schematic embodiment of a modified form.

Referring more particularly to Fig. 1 of the drawings, a main burner I0is supplied with fuel by a main fuel pipe l2 and the flow of fueltherein is under the separate control of a main control device, shown asa valve l4, and of a safety valve iii. The main valve 14 is manuallyoperable by the handle or dial l8 between the closed and open positionsindicated by the legend l8. A

pair of terminals 28' is carried on the body of the main valve l4 andthe legend 2| indicates the open and closed positions of a main switch22 incorporated in the main valve 14. As indicated by the legends l8 and2-1, when the dial I8 is moved to a position in which the main valve I4is open, then the main switch 22 is closed. When the dial I8 is moved toa position substantially 90 degrees from that described, then the mainvalve I4 is closed and the main switch 22 is open. It will be apparent,moreover, that the main valve it could embody a thermostaticallyoperated valve (not shown). Further details of a suitable form ofcombined main valve, thermostatic valve and electric switch aredisclosed in Weber Patent No. 2,276,751, March 1'7, 1942.

The safety valve I8 is an electromagnetic control means for the fuelflow in pipe i2. This valve is provided with a partition 24 having avalve seat 28 with an opening 28 therethroug'h controlled by a valvemember 28. A valve stem 30 for the valve member 28 projects exteriorlyof the safety valve l8 and carries a coil spring 82 serving to bias thevalve member 28 toward the valve seat 28. An armature member 84 iscarried on the exterior end of the valve stem 30 for cooperation with ahorseshoe magnet 38. When the valve member 28 is in the open positionshown in the drawing, the armature 84 is in its attracted positionagainst the pole faces of the magnet 38. A suitable coil or winding 88is provided for'the magnet 38 and connected in circuit with athermocouple 40 by wires 42 and 44.

The thermocouple 40 is located in proximity to the flame of apilotburner 48 and is adapted to be heated thereby. The pilot burner 46receives gaseous fuel from a conduit 48 connected with the valve seatopening 28 in the safety valve l8. In the arrangement shown the safetyvalve is provided with a reset stem 50 extending from. adjacent theunderside of the partitlon24 to the exterior of the safety valve i8 andbeing biased outwardly therefrom by a coil spring 52. The reset stem andvalve stem 30 are preferably in axial alignment and extend in oppositedirections from the valve seat opening 28 which i axially alignedtherewith;

The reset stem 50 carries a closure member 54 for the valve seat opening28. Formed on the reset stem 50 beyond the closure member 84 is aprojection 58 which is engageable with a projection 58 formed on thevalve stem 80 beyond the valve member- 28. When the reset stem 50 ismoved inwardly toward the valve seat 25 and the valve member 28 isseated thereon, the engagement ofthe projections 58 and 58 will serve toforce the valve member 28 away from the valve seat and position thearmature 34 in engagement with the pole faces of the magnet 88. At thesame time, the closure member 54 will close of! the valve seat opening28 thus preventing flow of fuel through the main fuel pipe l2 to themain burner II), but permitting fuel to flow in the conduit 48 to thepilot'burner 48. It will be apparent that the closure member 84 could bedispensed with and the resetting operation just described be conductedwhile fuel flows simultaneously in both the main fuel pipe I2 and thepilot conduit 48.

stem 50. Thus, the primary coil 84 of the transformer 60 serves toenergize the electromagnet causing movement of the plunger 82 intooperative engagement with the end of the reset stem 58 projecting fromthe safety valve IS. The plunger movement serves to operate the resetstem 58 in its resetting operation, previously described, when the coil84 is energized. A coil spring 51 carried by the plunger 52 serves toretract the latter when the coil 84 is inoperative. V

Associated with the primary coil 64 is a secondary coil 88 connected incircuit with an electric igniter 88 for the pilot burner 46 by means ofthe wires 10 and I2. It will be apparent that the safety valve l8 andits associated operating magnet 88 together with the transformer 80could be combined in a unitary construction and these elements have beenshown schematically in Fig. 1 of the drawings for illustrative purposeswithout intending any limitation to the exact form shown.

The electric circuit for the parts so far described may be traced fromone end of the primary coil 84 which is connected by a wire 14 to oneterminal of a. cutout 18, the other terminal of which is connected by awire 18 to one wire '88 of a source of current supply. This source maybe alternating current as supplied for domestic consumption. The cutoutI6 is preferably of the is adapted to open the circuit upon passage ofovercurrent occurring as will be hereinafter de-' scribed. The oppositeend of the primary coil 64 is connected by a wire 82 to one terminal 20of the main switch 22. The other terminal 28 is connected by a wire 84to one electrode 88 of an initially closed switching means 88 having theother electrode 90 thereof connected by a wire 82 to the other wire 94of the source of current supply.

The switching means embodies a timing element 88 of well-known formusually comprising a tube containing a pool of mercury and a restrictedorifice device 98 through which the mercur may flow when the timingelement 95 is tilted. Such tilting action may be performed through theemployment of a bell-crank lever I88 carrying the timing element 88 onone arm thereof and adapted to be moved by engagement of the oppositearm thereof with a cam element l82 carried by the dial l8.

' its open position. However, due to the time-delay incorporated in theswitching means 88, as described, the circuit through the electrodes 88and 80 isnot immediately opened. When, however, the dial I8 is beingoperated to open the main switch 22 and close the main valve 14, thenthe switching means 88 is preferably closed substantiallyinstantaneously. This instantaneous resetting of the switching means 88to initial closed position may be arranged by providing a relativelyunobstructed path for flow of the mercury around the orifice 98 to itsinitial position bridging the electrodes 86 and 98. It is to beunderstood that this is merely a diagrammatic illustration of atime-delay switch having instantaneous reset action and that theswitching means 88 is not necessarily limited to the mercury tube typeor, if of this type, need not be tilting, so long as the delayed openingand substantially instant closing features are incorporated.

When the dial i8 is moved to the position shown in Fig. l of thedrawings to close the main switch and open the main valve M, theswitching means 88 is thereupon moved from its initially closed positionto the open position shown in the drawing. Line voltage is then appliedto the primary 84 of the transformer 88 through the circuit hereinbeforedescribed causing the plunger 62 to be moved against the bias of thespring 61 into operative engagement with the reset stem 58. The valvemember 28 is consequently moved to its open position and the armature 84is moved into engagement with the pole faces of the magnet 88.

The opening of the valve member 23 of the safety valve l8, together withthe previously opened condition of the main valve l4, would allow fuelto flow to both the main burner l8 and the pilot burner 46 unless theclosure member 58 is incorporated in the safety valve l6. In the latterevent, the'fiow of fuel between the safety valve l6 and the main valve22 would be cut-off and only the pilot burner 46 would receive fuel.

The igniter 88 which is energized through the circuit described from thesecondary of the transformer 68 ignites the fuel flowing from the pilotburner 46 and produces a flame at this burner. At the end of the timedelay period of the switching means 88, which may be 18 seconds, thecircuit to the transformer 60 is opened by operation of this means, theplunger 62 is released by deenergization of the coil 64 and the igniter58 is also deenergized by the consequent deenergization of its circuitincluding the secondary coil 68.

The armature 34 is no longer held against the pole faces of the magnet36 by the mechanical action of the plunger 82 but is now held openelectrically by the action of the thermocouple 48 which is generatingcurrent for the coil 38 due to the heating effect of the pilot burnerflame. Consequently, the armature 34 is retained in attracted positionagainst the pole faces of the magnet 38. The closure member 54, ifincluded in the structure, no longer prevents the flow of fuel to themain burner Hi and such fuel is ignlted'by the flame from the pilotburner 45. The system is then in steady state operation under thecontrol of the thermocouple 48 alone.

In the event that the flame of the pilot burner 48 is extinguished, thethermocouple 40 cools and ceases to generatesufilcient current tomaintain the armature 34 in attracted position. The valve member 28 ofthe safety valve I6 thereupon closes and shutsoii' the flow of fuel toboth the main burner l8 and the pilot burner 46. Since the switchingmeans 88 is open-circuited the system will remain shut-off until thedial I8 is manually operated, first to close the main valve l4 and openthe switch 22 associated therewith, and then back to the position shownin the drawing wherein the main valve i4 is opened and the switch 22closed.

The system is thus of the non-recycling type with provision for completeshut-off of fuel to both the open the circuit controlled thereby and theigniter 88 simultaneously fails, then the cut out 18 would operate toopen the circuit after a short time, thus causing the safety valve I8 toclose.

In the embodiment shown in Fig2 there are various .parts which may beidentical with those shown and described in the previous embodiment andsimilar reference numerals have been applied thereto. Generally, thesystem disclosed in Fig. 2 differs from that disclosed in Fig. 1 in thatin the former there is no secondary winding on the plunger magnet, aseparate transformer is used and the switching means is provided with adouble time-delay instead of the single delay previously described. Aswill be apparent hereinafter, this modified arrangement permits ignitionof the pilot burner fuel before the main burner fuel is turned onwithout resorting to the use of a special closure member for the safetyvalve, as at 54 in the previously described embodiment. I 7

Referring, now more particularly to Fig. 2 of the drawing, the mainburner I receives gaseous fuel from a main fuel pipe I2 having a pilotconduit 13 connected thereto. A safety valve I1 is interposed in themain fuel pipe I2 between the connection for the pilot conduit I3 andthe main burner I0. The safety valve I'I embodies a partition 24 havinga valve seat 28 and a valve 6 seat opening 26 controlled by a valvemember 28.

A valve stem '30 is provided for the valve member 23 and a coil spring32 serves to bias the valve member 28 to closed position. An armature 34is carried on the projecting end of the valve stem 30 and is movablethereby into attracted relation with the pole faces of a horseshoemagnet 38 having acoil 38 associated therewith. A

thermocouple is located in proximity of thepilot burner 46 to be heatedby the flame thereof and is connected in circuit with the coil 38 by thewires 42 and 44.

The safety valve I'I isprovided with a reset stem movable into and outofthe valve seat opening 26 from the underside thereof for en-- gagementwith a projection 88 of the valve stem 30; The reset stem 50 is biasedaway from the valve stem 30 by a coil spring 52 as in the previousembodiment.

The operating means for the reset stem 80 comprises electromagneticmeans in the form of a horseshoe magnet I04 having an armature I08movable into and out of attracted relation with the pole faces thereofby an armature stem I08 which projects through the magnet into operativeengagement with the reset stem 50 and being axially aligned therewith. Acoil spring IIO carried by the armature stem I08 serves to bias thearmature I08 and stem I08 to thearmature disengaged position. A windingor coil II2 is provided for the magnet I04.

The main valve I4 of this embodiment may be identical with thatdisclosed in connection with Fig. 1 of the drawing but is located in themain fuel pipe I2 on the side of the pilot conduit I3 opposite thesafety valve II. The switching mechanism II4 which, as previouslyindicated. incorporates a double time-delay includes a pair of timingelements H8 and H8 in the form of mercury-containing tubes havingseparate pairs of electrodes I20-I22 and I24-I28, respectively. Therestricting oriflce I28 of the timing element II8 differs from therestricting orifice I30 of the element H8 in that a longer time-delayperiod is provided for the element H8. Such longer delay period may beapproximately three times that of the short delay which is about sixseconds. A suitable bell-crank lever I32 supports the timing elements H8and II8 on one arm thereon and has its opposite arm extending into thegatlhloaf movement of the cam I02 carried by the a The electricalcircuit for the reset means of this embodiment may be connected througha transformer I34 to asuitable source I38 of electric alternatingcurrent and may be traced by wire I38 connected at one end to thesecondary of the transformer I34 and at the opposite end to one terminal20 of the'electric switch 22 associated with the main valve I4. Theother terminal 20 is connected by a wire I33 to the electrode I20 and acommon wire I40 connects the electrodes I22 and I24. Electrode I28 isconnected by a wire I42 to one end of the igniter 80, the opposite endof the igniter being connected by a wire I44 to the secondary of thetransformer I34.

The coil .I I2 of the resetting electromagnet is connected at one end bya wire. I48 to the common wire I40 of the switching means H4 and theopposite end of the coil II2 isconnected bya wire I48 to the wire I42.It is apparent, therefore, that a.short-cir cuit will be established onthe coil I I2 by the shorter time'delayelement I I8 40 the main valve I4and close the main switch 22 associated therewith, the fuel flowsthrough the pilot conduit I3 to the pilot burner 48 but is preventedfrom flowing to the main burner I0 by the engagement of the valve member28 of the safety valve I! with the valve seat 25. The igniter 88 isenergized in the electrical circuit consisting of I the secondary oftransformer I34, wire I38, terminals 20, wire I38, electrodes I20I22,common wire I40, electrodes I24-.-I28, wire I42, igniter 88 and wire I44back to the secondary of transformer I34. The fuel flowing from thepilot burner 48 is ignited by the igniter 88 and the thermocouple 40becomes heated by the pilot burner flame. i

At the end of the flrst time-delay period flxed by operation of thetiming element I I8, the shortcircuit is removed from the coil H2 andthe current then flows by way of the wire I48. coil H2 and wire I48instead of by way of the electrodes I24--I26. The armature stem I03moves upwardly when the armature I08 is attracted by the energizedmagnet I04 and forces the reset stem into operative engagement with thevalve stem 30. The valve member 28 is moved off the valve seat 28 bythis engaging actionand the armature 34 is moved into engagement withthe pole faces of the magnet 38. The opening of the safety valve IIpermits fuel to flow to the main burner I0 where it is ignited by theflame of the pilot burner 48. I

At the expiration of the longer time-delay period fixed by operation ofthe timing element II8, both the igniter 88 and the coil II2 aredeenergized by the opening of the circuit previously traced. Thus, theforced pick-up condition of the safety valve i1 is eliminated but thevalve- 28 is held open as the armature 34 remains in attracted positionwith the pole faces of the magnet 36 due to the current generated by thethermocouple in which serves to energize the coil 38 of the magnet 36.The system is now in steady state operation under control of thethermocouple 40.

In the event that the flame of the pilot burner is extinguished, thenthe thermocouple ceases to generate current and the coil 38 becomesdeenergized releasing the armature 34 and closing the safety valve 81 bymovement of the valve member 28 to its seat. As such movement of thevalve member 28 controls only the flow of fuel to the main burner II),the flow of fuel through the pilot conduit l3 continues. The system isrestarted as in the previously described embodiment by rotating the diall8 to the valve-closed, switch-open position and then back to thevalveopen, switch-closed position illustrated in Fig. 2. This system isthus of the non-recycling type and does not provide a complete shut-offof fuel to both main and pilot burners by operation of the safety valve.

The invention described herein provides a relatively simple manner ofsafety control and ignition for gaseous fuel burners. The main burnerfuel is ignited within a few seconds of turning on the system which isadvantageous in oven installations. In steady state operation there isno possibility of disturbance due to line voltage variations or largestarting currents of other equipment connected to the same power supplyline as a separate thermoelectric current supply is relied upon. It willbe apparent that many changes can be made in the arrangement andcombination of parts and in the details of construction herein disclosedwithin the scope of the appended claims without departing from thespirit of the invention.

Iclaim:

1. A safety control system for fuel burners having main and pilotburners, comprising in combination, electromagnetic control means -8 Ihold the same in said fuel flow permitting position thereof after thesame has been reset by said reset means, and switching means having a:timing element connected in said energizin circuit means for renderingthe same inoperative upon expiration of a predetermined period followingestablishment thereof and during which said control means has had timeto become energized.

3. A safety control andv ignition system for fuel burners having mainand pilot burners, comprising in combination, an electric igniter forthe pilot burner, electromagnetic control means biased to a position forpreventing flow of fuel to at least the main burner, electromagneticreset means operable when energized-for overcoming said bias andresetting said control means 1 in a fuel flow permitting position, meansfor csbiased to a position for preventing flow 'of' ,said fuel flowpermittingposition thereof after the same has been reset by said resetmeans. and switching means having a timing element connected in saidcircuit means for rendering the same inoperative upon expiration of apredetermined period following establishment thereof and during whichsaid control means has had tim to become energized.

2. A'safety control and ignition system for fuel burners having main andpilot burners, comprising in combination, an electric igniter for thepilot burner, electromagnetic control means biased to a position forpreventing flow of fuel to at least the main burner, electromagneticreset means operable when energized for overcoming said bias andresetting said control means in a fuel flow permitting position, meansfor establishing an energizing circuit meansincluding said igniter andsaid reset means, means respontablishing an energizing circuit meansincluding said igniter and said reset means, means responsive to thepresence of a flame at the pilot burner for energizing said controlmeans sufficiently to hold the same in said fuel flow permittingposition thereof after the same has been reset by said reset means, andinitially closed-switching means having a timing element connected insaid energizing circuit means, said switching means being operable forcausing said timing element to open said circuit and rendering the sameinoperative upon expiration of a predetermined period followingestablishment thereof and thereby causing deenergization of said resetmeans and igniter while said control means has had time to becomeenergized.

4. A safety control and ignition system for fuel burners having main'and pilot burners and means for supplying fuel thereto, comprising incombination, a main control device operable between fuel flow preventingand permitting positions for controlling the fuel supply from the supplymeans to at least the main burner, an electric igniter for the pilotburner, electromagnetic control means also controlling the fuel supplyfrom the supply means to at least the main burner and being biased to afuel flow preventing position, electromagnetic reset means operable whenenergized for overcoming said bias and resetting said control means in afuel flow permitting position, means for establishing an energizingcircuit, means including said igniter and said reset means, meansresponsive to the presence of a flame at the pilot burner for energizingsaidcontrol means sufllciently to hold the same in said fuel flowpermitting position thereof after the same has been reset by said resetmeans, initially closed switching means having a timing elementconnected in said energizing circuit means for rendering the sameinoperative upon expiration of a predetermined period followingoperation of said switching means, an initially open main switch forsaid sive to the presence of a flame at the pilot burner circuit means,and means associated with said control device for operating the same tofuel flow permitting position and concomitantly closing said main switchand operating said switching means to cause deenergization of said resetmeans and igniter upon expiration of saidperiod during which saidcontrol means has had time to become energized.

5. A safety control and ignition system for fuel burners having main andpilot burners, comprising in combination, electromagnetic, control meansbiased to a position for preventing flow of fuel to at least the mainburner, reset means including a transformer having a coil and a plungerasses-is i operable when energized for overcoming said bias andresetting said control means in a fuel flow permitting position, meansfor establishing an energizing circuit means for said reset means, anelectric igniter for the pilot burner including a secondary coil of saidtransformer, means responsive to the presence of a flame at the pilotburner for energizing said control means sufficiently to hold the samein said fuel flow permitting position thereof after the same has beenreset by said reset means, and switching means having a timing elementconnected in said energizing circuit means for rendering the sameinoperative upon expiration of a predetermined period followingestablishment thereof and during which said control means has had timeto become energized.

6. A safety control and ignition system for fuel burners having main andpilot burners and means for supplyingfuel thereto, comprising incombination, electromagnetic control means operable between fuel flowpreventing and permitting positions for controlling the fuel supply fromthe supply means to the burners and being biased to a fuel flowpreventing position, a main control device interposed between saidcontrol means and the main burner for controlling the fuel supply to themain burner, reset means including a transformer having a coil and aplunger operable when energized for overcoming said bias and resettingsaid control means in a fuel flow permitting position, means forestablishing an energizing circuit means for said reset means, anelectric igniter for the pilot burner including a secondary coil of saidtransformer, means responsive to the presence of a flame at the pilotburner for energizing said control means sufiiciently to hold the samein said fuel flow permitting position thereor after the same has beenreset by said reset means, initially closed switching means having atiming element connected in said energizing circuit means for renderingthe same inoperative upon expiration of a predetermined period followingoperation of said switching means, an initially open main switch forsaid circuit means, and means associated with said control device foroperatingthe same to fuel flow permitting position and concomitantlyclosing said main switch and operating said switching means to causedeenergization of said reset means and igniter upon expiration of saidperiod during which said con trolmeans has had time to become energized.

'7. A safety control and ignition system for fuel burners having mainand pilot burners, comprise ing in combination, an electric lgniter forthe pilot burner, electromagnetic control means-for the main burnerbiased to a fuel flow preventing position, electromagnetic reset meansoperable when energized for overcoming said bias and resetting saidcontrol means in a fuel flow'permitting position, means for establishingan energizing circuit means including said lgniter and said reset means,means responsive to the presence of a flame at the pilot burner forenergizing said control means sufficiently to hold the same in said fuelflow permitting position thereof after the same has been reset by saidreset means, and switching ul in which said control means has time tobecome en said circui-tmeans and during tins operation is completed.

8. A safety control and ignition system for fuel burners having main andpilot burners, comprising in combination, an electric igniter for thepilot burner, a thermocouple located to be heated by a flame at thepilot burner, electromagnetic control means connected in circuit withsaid thermocouple and adapted to prevent supply of fuel to the mainburner when said fiame is extinguished, means for establishing anenergizing circuit which said resetmeans from a source other than saidthermocouple, means in said energizing circuit means and operable whenenergized for resetting said control means to supply fuel to the mainburner, and switching means in said energizing circuit means adapted torenderisaid reset means inoperative for a predetermined period followingestablishment of said circuit means and during which said control meanshas time to become energized and thereafter render said energizingcircuit means inoperative upon completion of said resetting operation.

9. A safety control and ignition system for fuel burners having main andpilot burners and means for supplying fuel thereto, comprising incombination, a main control device operable between fuel flow preventingand permitting positions for controlling the fuel supply from the supplymeans I to the burners, an electric isniter for the pilot burner.electromagnetic control means operable between fuel flow preventing andpermitting positions for controlling the fuel supply from said maincontrol device to the main burner, said control means being biased tosaid fuel flow preventing position, electromagnetic reset means operablewhen energized for overcoming said bias and resetting said control meansin a fuel flow permitting position, means for establishing an energizingcircuit means including said igniter and said reset means, meansresponsive to the presence of a flame at the pilot burner for energizingsaid control means sufficiently to hold the same in said fuel flowpermitting position thereof after the same has been reset by said'resetmeans, initially closed switching means having a pair of timing elementsconnected in said energizing circuit means, one said element beingoperable for establishing a short-circuit on said rev set means for apredetermined period following establishment of said circuit means andduring ergized, and the other said element being operable for renderingsaid energizing circuit inoperative after a further predetermined periodfollowing establishment of said circuit means and during which saidresetting operation is completed,

an initially open main switch for said energizing circuit means, andmeans associated with said control device for operating the same to fuelflow permitting position and concomitantly closing said main switch andoperating said switching means having a pair of timing elementsconnected in said energizing circuit means, one said elementestablishing a short-circuit on said reset means for a predeterminedperiod following establishment of said circuit means and during whichsaid control means has time to become energized, and

means.

10. A safety control system for fuel burners having main and pilotburners, comprising in combination, electromagnetic control means biasedto a position for preventing flow of fuel to at least the main burner,reset means including a transformer having a plunger operable whenenergized for overcoming said bias and resetting said control means in afuel flow permitting pt, sition, means for establishing an energizingcircuit means for'said resetmeans. means responsive to the presence of aflame at the pilot burner for energizing said control means sufficiently11.. In a control system for fuel burning apparatus having a source ofelectrical energy. the

combination with electromagnetic control means biased to a fuel flowpreventing position, thermoelectric means located to be heated by theburning fuel for energizing said control means sufliciently to hold thesame in a fuel flow permitting position but being incapable of actuatingthe same to said position, of means for establishing a circuit meansconnected to said source and including electromagnetic reset meansoperable when energized for overcoming said bias and actuating saidcontrol means to said fuel flow permitting position, and initiallyclosed switching means having a timing element connected in said circuitmeans, said switching means being operable for causing said timingelement to open said circuit means upon expiration of a predeterminedperiod following establishment thereof and during which said controlmeans has had time to become energized.

12 In a control system for fuel burning apparatus having a source ofelectrical energy, the combination with electromagnetic control meansbiased to a fuel flow preventing position, thermoelectric means locatedto be heated by thebuming fuel for energizing said control meanssufficiently to hold the same in a fuel flow permitting position butbeing incapableiof actuating the same to said position, of means. forestablishing a circuit means connected to said source and includingelectromagnetic reset means operable when energized for overcoming saidbias and actuating said control means to said fuel flow permittingposition, and manually operable switching means having a timing elementconnected in said circuit means and adapted for delayed antion to openposition but substantially instantaneous action to closed position, saidswitching means being initially closed and being operable for causingsaid timing element to open said clr- 'cui't means upon expiration of apredetermined periodfollowing establishment thereof and during whichsaid control means has had time to become energized. I

13. In a safety control system for fuel burners having main and pilotburners and a source of electrical energy, the combination withelectromagnetic control means biased to a position for preventing flowof fuel to both the main and pilot burners, thermoelectric means locatedto said switching means being operable for causing said timing elementto open said circuit upon expiration of a predetermined period followingestablishment thereof and during which said control means has hadtime tobecome energized, saidvflow interrupting means being renderedinoperative when said circuit means is opened and said control means isin position to shut-off the flow of fuel to both the main and pilotburners upon cessation of said flame.

14. In a safety control system for fuel burners having a source ofelectrical energy, the combination with a main control device operablebetween fuelfiow preventing and permitting positions, electromagneticcontrol means also operable between said positions and being biased to afuel flow preventing position, thermoelectric means located to be heatedby the burning fuel for energizing said control means sufficlently tohold the same in a fuel fiow permitting position but being incapable ofactuating the same to said position, of' means for establishing acircuit means connected to said source and including electromagneticreset means operable when energized for overcoming said bias andactuating said control means to said fuel flow permitting position,initially closed switching means having a timing element connected insaid circuit means and adapted for delayed action. to open position butsubstantially instantaneous action to closed position; said switchingmeans being operable for causing said timing element to open saidcircuit means upon expiration-of a predetermined period followingestablishment thereof and during which said control means has had timeto become energized, an initially open main switch for said circuit, andmeans associated with said control device for operating the same to fuelflow permitting position and concomitantly closing said main switch andoperating said switching means. 7 v

15. In a control device, the combination with electromagnetic meanshaving an armature and magnet, holding "means operative for energizingsaid magnet sufiiciently to retain said armature in attracted positionrelative to said magnet but insufllciently to cause said armature toassume said position, of means to reset said armature in said positionand thereafter become inoperative while said holding means is operative,said reset means comprising a source of electrical energy, a transformerhaving primary and secondary coils, reciprocable means operable inresponse to energization of said transformer for causing said armatureto assume said attracted position, means for establishing a circuitmeans including said source and. one of said coils, and initially closedswitching means having a timing element connected in saidcircuit meansand operable for a be heated by a flame at the pilot burner forenergizing said control means sufficiently to hold i the same in a fuelflow permitting position but being incapable of actuating the sametosaid position, of a means for establishing a circuit means connected tothe. source and including electromagnetic reset means operable whenenopening the same upon expiration of a predeter- REFERENCES CITED 'Ihefollowing references are of record in the file of this patent:

UNITED S TATES PATENTS Number Name Date 2,118,886 Joesting May 31, 19382,189,829

Wunsch et a1. Feb. 13, 1940

